The basic penicillin nucleus is a 4-thia-1-azabicyclo[3.2.0]heptan-7-one ring system having the skeletal structure: ##STR1## Compounds having this ring system have been the object of intense research and numerous scientific articles and patents over the past two decades.
Within the last few years, attention has been directed to the synthesis of compounds having analogous ring systems. Among these penicillin analogs are 1-azabicyclo[3.2.0]heptane-7-one systems [Moll et al., Z. Naturforsch B 24:942 (1969); Earle et al., J. Chem. Soc. C 2093 (1969) and Lowe et al., i J. Chem. Soc. Chem. Comm. 328 (1973)]; 4-oxa-1-azabicyclo[3.2.0]heptan-7-one systems [Deshpande et al., J. Chem. Soc. C 1241 (1966); Wolfe et al., Can. J. Chem 50:2902 (1972); Golding et al., J. Chem. Soc. Chem. Comm. 293 (1973); German Offenlegungschriften 2,219,601, 2,356,862 and 2,411,856; Japanese Pat. No. 9,007,263 and Netherlands Pat. No. 7,313,896]; 1,4-diazabicyclo[3.2.0]heptan-7-one systems [Bose et al., J. Org. Chem. 38:3437 (1973) and German Offenlegungschrift 2,219,601] and a 3-thia-1-azabicyclo[3.2.0]heptan-7-one system [Bose et al., J. Chem. Soc. C 188 (1971)].
Compounds containing the 1,3-diazabicyclo[3.2.0]heptan-7-one nucleus have now been prepared by a totally synthetic method.